Rho gtpase activating protein 21Rho GTPase activating protein 21 is a protein that in humans is encoded by the ARHGAP21 gene.FunctionARHGAP21 functions preferentially as a GTPase-activating protein for CDC42 and regulates the ARP2/3 complex and F-actin dynamics at the Golgi through control of CDC42 activity. There is little scientific literature on ARHGAP21, but recent reviews highlighted that it plays an important role in cytoskeletal processes in cancer, substance transport within the cell, and insulin secretion